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/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef ENDGAME_H_INCLUDED
#define ENDGAME_H_INCLUDED
#include <memory>
#include <string>
#include <type_traits>
#include <unordered_map>
#include <utility>
#include "position.h"
#include "types.h"
/// EndgameCode lists all supported endgame functions by corresponding codes
enum EndgameCode {
EVALUATION_FUNCTIONS,
KNNK, // KNN vs K
KNNKP, // KNN vs KP
KXK, // Generic "mate lone king" eval
KBNK, // KBN vs K
KPK, // KP vs K
KRKP, // KR vs KP
KRKB, // KR vs KB
KRKN, // KR vs KN
KQKP, // KQ vs KP
KQKR, // KQ vs KR
SCALING_FUNCTIONS,
KBPsK, // KB and pawns vs K
KQKRPs, // KQ vs KR and pawns
KRPKR, // KRP vs KR
KRPKB, // KRP vs KB
KRPPKRP, // KRPP vs KRP
KPsK, // K and pawns vs K
KBPKB, // KBP vs KB
KBPPKB, // KBPP vs KB
KBPKN, // KBP vs KN
KPKP // KP vs KP
};
/// Endgame functions can be of two types depending on whether they return a
/// Value or a ScaleFactor.
template<EndgameCode E> using
eg_type = typename std::conditional<(E < SCALING_FUNCTIONS), Value, ScaleFactor>::type;
/// Base and derived functors for endgame evaluation and scaling functions
template<typename T>
struct EndgameBase {
explicit EndgameBase(Color c) : strongSide(c), weakSide(~c) {}
virtual ~EndgameBase() = default;
virtual T operator()(const Position&) const = 0;
const Color strongSide, weakSide;
};
template<EndgameCode E, typename T = eg_type<E>>
struct Endgame : public EndgameBase<T> {
explicit Endgame(Color c) : EndgameBase<T>(c) {}
T operator()(const Position&) const override;
};
/// The Endgames namespace handles the pointers to endgame evaluation and scaling
/// base objects in two std::map. We use polymorphism to invoke the actual
/// endgame function by calling its virtual operator().
namespace Endgames {
template<typename T> using Ptr = std::unique_ptr<EndgameBase<T>>;
template<typename T> using Map = std::unordered_map<Key, Ptr<T>>;
extern std::pair<Map<Value>, Map<ScaleFactor>> maps;
void init();
template<typename T>
Map<T>& map() {
return std::get<std::is_same<T, ScaleFactor>::value>(maps);
}
template<EndgameCode E, typename T = eg_type<E>>
void add(const std::string& code) {
StateInfo st;
map<T>()[Position().set(code, WHITE, &st).material_key()] = Ptr<T>(new Endgame<E>(WHITE));
map<T>()[Position().set(code, BLACK, &st).material_key()] = Ptr<T>(new Endgame<E>(BLACK));
}
template<typename T>
const EndgameBase<T>* probe(Key key) {
auto it = map<T>().find(key);
return it != map<T>().end() ? it->second.get() : nullptr;
}
}
#endif // #ifndef ENDGAME_H_INCLUDED
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